后端程序员都知道,在Web系统中,分页是一种常见的功能,我之前写的分页方法都比较麻烦,移植性也不高,这就很不乐观了。作为一个积极开朗的程序员,怎么能不去了解PageHelper分页插件呢?PageHelper是国内非常优秀的一款开源的mybatis分页插件,它支持基本主流与常用的数据库,一致支持mysql、oracle、mariaDB、DB2、SQLite、Hsqldb等。OK接下来就一起来了解了解PageHelper分页插件!
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首先,推荐两个PageHelper分页插件项目地址,这里面有中文教程:
github 项目
gitosc 项目至于怎么使用我想上面提供的两个项目讲的绝逼讲的比我清楚,下面直接进入PageHelper使用实战
首先,集成引入分页插件有下面2种方式,一种是直接下jar包一种是mawen依赖, 推荐使用 Maven 方式 。
方法一: 直接下载jar包
jar包下载地址 ,由于使用了sql 解析工具,你还需要下载 jsqlparser.jar
方法二: Maven添加依赖
<dependency> <groupId>com.github.pagehelper</groupId> <artifactId>pagehelper</artifactId> <version>5.1.2</version> </dependency>
我这里就采用方法二maven依赖
情况一
:如果是 mybatis单独使用PageHelper分页插件 的时候,就需要在xml配置中添加如下代码:
<!-- plugins在配置文件中的位置必须符合要求,否则会报错,顺序如下properties?, settings?, typeAliases?, typeHandlers?, objectFactory?,objectWrapperFactory?, plugins?, environments?, databaseIdProvider?, mappers? --> <!-- com.github.pagehelper为PageHelper类所在包名 --> <plugins> <!-- 使用下面的方式配置参数,推荐的两个项目中有所有的参数介绍 --> <plugin interceptor="com.github.pagehelper.PageInterceptor"> <property name="param1" value="value1"/> </plugin> </plugins>
情况二
:显然,我是这个是ssm项目, mybatis是交由spring的IOC容器管理 的,就需要在spring的xml配置中添加如下代码(创建工厂中添加):
<!-- 把交给IOC管理 SqlSessionFactory --> <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean"> <property name="dataSource" ref="dataSource"/> <!-- 传入PageHelper的插件 --> <property name="plugins"> <array> <!-- 传入插件的对象 --> <bean class="com.github.pagehelper.PageInterceptor"> <property name="properties"> <props> <prop key="helperDialect">oracle</prop> <prop key="reasonable">true</prop> </props> </property> </bean> </array> </property> </bean>
下面用一个图来分析一下两个参数作用:
更多情况请参考上面推荐的项目~
上面我们配置完了,至于为什么从controller代码开始是因为controller调用service嘛,这样编写代码更方便快捷!为了看出差别,未分页的controller代码方法如下:
@Controller @RequestMapping("/orders") public class OrdersController { @Autowired private IOrdersService ordersService; //查询所有orders未分页 @RequestMapping("/findAll.do") public ModelAndView findAll() { ModelAndView mv = new ModelAndView(); List<Orders> ordersList = ordersService.findAll(); mv.addObject("ordersList", ordersList); mv.setViewName("orders-list"); return mv; } }
而采用了分页代码则是如下:
//采用分页代码方法 @RequestMapping("/findAll.do") public ModelAndView findAll(@RequestParam(name="page",required = true,defaultValue = "1")int page,@RequestParam(name="size",required = true,defaultValue = "4")int size ) { ModelAndView mv = new ModelAndView(); List<Orders> ordersList = ordersService.findAll(page,size); //PageInfo就是一个分页Bean PageInfo pageInfo =new PageInfo(ordersList); mv.addObject("pageInfo", pageInfo); mv.setViewName("orders-list"); return mv; }
可以发现多了两个参数分别是 page
和 size
public interface IOrdersService { List<Orders> findAll(int page,int size); }
在执行sql之前(ServiceImpl),使用PageHelper分页,参数 pageNum
是页码值 参数 pageSize
代表是每页显示条数。在ServiceImpl中,使用PageHelper分页操作代码如下:
@Service public class OrdersServiceImpl implements IOrdersService { @Autowired private IOrdersDao ordersDao; @Override public List<Orders> findAll(int page,int size) { //参数pageNum 是页码值 参数pageSize 代表是每页显示条数 PageHelper.startPage(page, size); return ordersDao.findAll(); } }
特别注意:在编写PageHelper分页代码时的 PageHelper.startPage(page, size)
这一句必须写在查询方法的上一句,中间不能添加任何代码,否则失效!
没有更改的jsp页面代码,普通查询关键更改代码块,注意这里接收数据为 ordersList
<c:forEach items="${ordersList}" var="orders"> <tr> <td><input name="ids" type="checkbox"></td> ... <td>...</td> </td> </tr> </c:forEach>
这下面的代码则是未分页逻辑代码
<div class="box-tools pull-right"> <ul class="pagination"> <li> <a href="#" aria-label="Previous">首页</a> </li> <li><a href="#">上一页</a></li> <li><a href="#">1</a></li> <li><a href="#">2</a></li> <li><a href="#">3</a></li> <li><a href="#">4</a></li> <li><a href="#">5</a></li> <li><a href="#">下一页</a></li> <li> <a href="#" aria-label="Next">尾页</a> </li> </ul> </div> </div>
更改后的jsp页面代码,分页查询的关键更改代码块,注意这里接收数据为 ordersList.list
<c:forEach items="${ordersList.list}" var="orders"> <tr> <td><input name="ids" type="checkbox"></td> ... <td>...</td> </td> </tr> </c:forEach>
这下面的代码则是分页逻辑代码
<div class="box-tools pull-right"> <ul class="pagination"> <li> <a href="${pageContext.request.contextPath}/orders/findAll.do?page=1&size=${pageInfo.pageSize}" aria-label="Previous">首页</a> </li> <li><a href="${pageContext.request.contextPath}/orders/findAll.do?page=${pageInfo.pageNum-1}&size=${pageInfo.pageSize}">上一页</a></li> <c:forEach begin="1" end="${pageInfo.pages}" var="pageNum"> <li><a href="${pageContext.request.contextPath}/orders/findAll.do?page=${pageNum}&size=${pageInfo.pageSize}">${pageNum}</a></li> </c:forEach> <li><a href="${pageContext.request.contextPath}/orders/findAll.do?page=${pageInfo.pageNum+1}&size=${pageInfo.pageSize}">下一页</a></li> <li> <a href="${pageContext.request.contextPath}/orders/findAll.do?page=${pageInfo.pages}&size=${pageInfo.pageSize}" aria-label="Next">尾页</a> </li> </ul> </div> </div>
//PageInfo就是一个分页Bean PageInfo pageInfo =new PageInfo(ordersList);
为了能看到上面的pageInfo源代码,我就把代码贴在下面了
package com.github.pagehelper; import java.io.Serializable; import java.util.Collection; import java.util.List; public class PageInfo<T> implements Serializable { private static final long serialVersionUID = 1L; private int pageNum; private int pageSize; private int size; private int startRow; private int endRow; private long total; private int pages; private List<T> list; private int prePage; private int nextPage; private boolean isFirstPage; private boolean isLastPage; private boolean hasPreviousPage; private boolean hasNextPage; private int navigatePages; private int[] navigatepageNums; private int navigateFirstPage; private int navigateLastPage; public PageInfo() { this.isFirstPage = false; this.isLastPage = false; this.hasPreviousPage = false; this.hasNextPage = false; } public PageInfo(List<T> list) { this(list, 8); } public PageInfo(List<T> list, int navigatePages) { this.isFirstPage = false; this.isLastPage = false; this.hasPreviousPage = false; this.hasNextPage = false; if (list instanceof Page) { Page page = (Page)list; this.pageNum = page.getPageNum(); this.pageSize = page.getPageSize(); this.pages = page.getPages(); this.list = page; this.size = page.size(); this.total = page.getTotal(); if (this.size == 0) { this.startRow = 0; this.endRow = 0; } else { this.startRow = page.getStartRow() + 1; this.endRow = this.startRow - 1 + this.size; } } else if (list instanceof Collection) { this.pageNum = 1; this.pageSize = list.size(); this.pages = this.pageSize > 0 ? 1 : 0; this.list = list; this.size = list.size(); this.total = (long)list.size(); this.startRow = 0; this.endRow = list.size() > 0 ? list.size() - 1 : 0; } if (list instanceof Collection) { this.navigatePages = navigatePages; this.calcNavigatepageNums(); this.calcPage(); this.judgePageBoudary(); } } private void calcNavigatepageNums() { int i; if (this.pages <= this.navigatePages) { this.navigatepageNums = new int[this.pages]; for(i = 0; i < this.pages; ++i) { this.navigatepageNums[i] = i + 1; } } else { this.navigatepageNums = new int[this.navigatePages]; i = this.pageNum - this.navigatePages / 2; int endNum = this.pageNum + this.navigatePages / 2; int i; if (i < 1) { i = 1; for(i = 0; i < this.navigatePages; ++i) { this.navigatepageNums[i] = i++; } } else if (endNum > this.pages) { endNum = this.pages; for(i = this.navigatePages - 1; i >= 0; --i) { this.navigatepageNums[i] = endNum--; } } else { for(i = 0; i < this.navigatePages; ++i) { this.navigatepageNums[i] = i++; } } } } private void calcPage() { if (this.navigatepageNums != null && this.navigatepageNums.length > 0) { this.navigateFirstPage = this.navigatepageNums[0]; this.navigateLastPage = this.navigatepageNums[this.navigatepageNums.length - 1]; if (this.pageNum > 1) { this.prePage = this.pageNum - 1; } if (this.pageNum < this.pages) { this.nextPage = this.pageNum + 1; } } } private void judgePageBoudary() { this.isFirstPage = this.pageNum == 1; this.isLastPage = this.pageNum == this.pages || this.pages == 0; this.hasPreviousPage = this.pageNum > 1; this.hasNextPage = this.pageNum < this.pages; } public int getPageNum() { return this.pageNum; } public void setPageNum(int pageNum) { this.pageNum = pageNum; } public int getPageSize() { return this.pageSize; } public void setPageSize(int pageSize) { this.pageSize = pageSize; } public int getSize() { return this.size; } public void setSize(int size) { this.size = size; } public int getStartRow() { return this.startRow; } public void setStartRow(int startRow) { this.startRow = startRow; } public int getEndRow() { return this.endRow; } public void setEndRow(int endRow) { this.endRow = endRow; } public long getTotal() { return this.total; } public void setTotal(long total) { this.total = total; } public int getPages() { return this.pages; } public void setPages(int pages) { this.pages = pages; } public List<T> getList() { return this.list; } public void setList(List<T> list) { this.list = list; } /** @deprecated */ @Deprecated public int getFirstPage() { return this.navigateFirstPage; } /** @deprecated */ @Deprecated public void setFirstPage(int firstPage) { this.navigateFirstPage = firstPage; } public int getPrePage() { return this.prePage; } public void setPrePage(int prePage) { this.prePage = prePage; } public int getNextPage() { return this.nextPage; } public void setNextPage(int nextPage) { this.nextPage = nextPage; } /** @deprecated */ @Deprecated public int getLastPage() { return this.navigateLastPage; } /** @deprecated */ @Deprecated public void setLastPage(int lastPage) { this.navigateLastPage = lastPage; } public boolean isIsFirstPage() { return this.isFirstPage; } public void setIsFirstPage(boolean isFirstPage) { this.isFirstPage = isFirstPage; } public boolean isIsLastPage() { return this.isLastPage; } public void setIsLastPage(boolean isLastPage) { this.isLastPage = isLastPage; } public boolean isHasPreviousPage() { return this.hasPreviousPage; } public void setHasPreviousPage(boolean hasPreviousPage) { this.hasPreviousPage = hasPreviousPage; } public boolean isHasNextPage() { return this.hasNextPage; } public void setHasNextPage(boolean hasNextPage) { this.hasNextPage = hasNextPage; } public int getNavigatePages() { return this.navigatePages; } public void setNavigatePages(int navigatePages) { this.navigatePages = navigatePages; } public int[] getNavigatepageNums() { return this.navigatepageNums; } public void setNavigatepageNums(int[] navigatepageNums) { this.navigatepageNums = navigatepageNums; } public int getNavigateFirstPage() { return this.navigateFirstPage; } public int getNavigateLastPage() { return this.navigateLastPage; } public void setNavigateFirstPage(int navigateFirstPage) { this.navigateFirstPage = navigateFirstPage; } public void setNavigateLastPage(int navigateLastPage) { this.navigateLastPage = navigateLastPage; } public String toString() { StringBuffer sb = new StringBuffer("PageInfo{"); sb.append("pageNum=").append(this.pageNum); sb.append(", pageSize=").append(this.pageSize); sb.append(", size=").append(this.size); sb.append(", startRow=").append(this.startRow); sb.append(", endRow=").append(this.endRow); sb.append(", total=").append(this.total); sb.append(", pages=").append(this.pages); sb.append(", list=").append(this.list); sb.append(", prePage=").append(this.prePage); sb.append(", nextPage=").append(this.nextPage); sb.append(", isFirstPage=").append(this.isFirstPage); sb.append(", isLastPage=").append(this.isLastPage); sb.append(", hasPreviousPage=").append(this.hasPreviousPage); sb.append(", hasNextPage=").append(this.hasNextPage); sb.append(", navigatePages=").append(this.navigatePages); sb.append(", navigateFirstPage=").append(this.navigateFirstPage); sb.append(", navigateLastPage=").append(this.navigateLastPage); sb.append(", navigatepageNums="); if (this.navigatepageNums == null) { sb.append("null"); } else { sb.append('['); for(int i = 0; i < this.navigatepageNums.length; ++i) { sb.append(i == 0 ? "" : ", ").append(this.navigatepageNums[i]); } sb.append(']'); } sb.append('}'); return sb.toString(); } }
到这里,基本就OK了,我再次强调我推荐的那两个项目,那里面讲的很详细大佬写的,强调完毕,挥爪~